The 3.5-mile march will start from two positions at noon: Embankment, proceeding down Whitehall, past Parliament, and Gower Street.

They will converge at Piccadilly Circus.

The model Kate Moss and British designer Alexander McQueen will be leading a protest group from the fashion world.

Police advice to marchers

Be patient

Wear warm clothes

Bring snacks

Carry a radio and monitor events on local radio

The march, which has been organised by Stop the War Coalition, the
Campaign for Nuclear Disarmament and the Muslim Association of Britain, will culminate in a rally at Hyde Park where a succession of speakers, including former US presidential candidate Reverend Jesse Jackson, will take to a stage near Speakers' Corner.

The crowd will be entertained by music from former Blur
frontman Damon Albarn and the singer Ms Dynamite.

Glasgow rally

The prime minister's office said in a statement that he "respected the views" of those taking part in the march but suggested the gesture would make little difference to government policy.

"The way to prevent any military conflict is for Saddam Hussein to co-operate
and fulfil his obligations as set out by the whole of the international
community as embodied by the United Nations," said Tony Blair's official spokesman.

All police leave in the capital has been cancelled and 3,500 officers drafted in from the Met, the City of London force and British Transport Police to control the event.

Roads around the route will be closed to traffic from 1030 GMT until the rally finishes at around 1700.

The London march is one of many being held in cities around the world.

In Glasgow, protesters will start their rally early to coincide with Tony Blair's speech to the Labour Party spring conference in the city.

In London on Friday, five anti-war demonstrators chained themselves to a pink heart outside the gates of Downing Street.